Preparation of sulfur-containing organosilicon compounds using a buffered phase transfer catalysis process

ABSTRACT

A process for the production of sulfur containing organosilicon compounds of the formula: 
     
       
         (RO) 3−m R m Si—Alk—S n —Alk—SiR m (OR) 3−m   
       
     
     where 
     R is independently a monovalent hydrocarbon of 1 to 12 carbon atoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms; 
     m is an integer of 0 to 2, n is a number from 1 to 8; 
     based on phase transfer catalysis techniques is disclosed. The process comprises reacting: 
     (A) a sulfide compound having the formula M 2 S n  or MHS, 
     where H is hydrogen, M is ammonium or an alkali metal, 
     n is as defined above, with 
     (B) a silane compound of the formula; 
     
       
         (RO) 3−m R m Si—Alk—X 
       
     
     where X is Cl, Br or I, and m is the same as above, and optionally, 
     (C) sulfur 
     in the presence of a phase transfer catalyst and an aqueous phase containing a buffer. 
     The improvement of the present invention is characterized by adding a buffer to the aqueous phase, which minimizes or prevents gelling of the sulfur containing organosilicon compounds. The present invention also teaches a process for the production of sulfur containing organosilicon compounds by controlling the pH of the aqueous phase.

FIELD OF THE INVENTION

This invention relates to a process for the production of sulfurcontaining organosilicon compounds by phase transfer catalysistechniques. The process involves reacting a sulfide, and optionallysulfur, with a silane compound in the presence of a phase transfercatalyst and aqueous phase containing a buffer.

BACKGROUND OF THE INVENTION

Sulfur containing organosilicon compounds are useful as reactivecoupling agents in a variety of commercial applications. In particular,sulfur containing organosilicon compounds have become essentialcomponents in the production of tires based on rubber vulcanatescontaining silica. The sulfur containing organosilicon compounds improvethe physical properties of the rubber vulcanates containing silicaresulting in automotive tires with improved abrasion resistance, rollingresistance, and wet skidding performance. The sulfur containingorganosilicon compounds can be added directly to the rubber vulcanatescontaining silica, or alternately, can be used to pre-treat the silicaprior to addition to the rubber vulcanate composition.

Numerous methods have been described in the art for the preparation ofsulfur containing organosilicon compounds. For example, U.S. Pat. No.5,399,739 by French et al. describes a method for makingsulfur-containing organosilanes by reacting an alkali metal alcoholatewith hydrogen sulfide to form an alkali metal hydrosulfide, which issubsequently reacted with an alkali metal to provide an alkali metalsulfide. The resulting alkali metal sulfide is then reacted with sulfurto provide an alkali metal polysulfide which is then finally reactedwith a silane compound of the formula X—R²—Si(R¹)₃, where X is eitherchlorine or bromine to produce the sulfur-containing organosilane.

U.S. Pat. Nos. 5,466,848, 5,596,116, and 5,489,701 describe processesfor the preparation of silane polysulfides. The '848 patent process isbased on first producing sodium sulfide by the reaction of hydrogensulfide with sodium ethoxylate. The sodium sulfide is then reacted withsulfur to form the tetrasulfide, which is subsequently reacted withchloropropyltriethoxysilane to form 3,3′-bis (triethoxysilylpropyl)tetrasulfide. The '116 patent teaches a process for the preparation ofpolysulfides, without the use of hydrogen sulfide, by reacting a metalalkoxide in alcohol with elemental sulfur, or by reacting sodium metalwith elemental sulfur and an alcohol, with a halohydrocarbylalkoxysilanesuch as chloropropyltriethoxysilane. The '701 patent claims a processfor the preparation of silane polysulfides by contacting hydrogensulfide gas with an active metal alkoxide solution and subsequentlyreacting the reaction product with a halohydrocarbylalkoxysilane such aschloropropyltriethoxysilane.

U.S. Pat. No. 5,892,085 describes a process for the preparation of highpurity organosilicon disulphanes. U.S. Pat. No. 5,859,275 describes aprocess for the production of bis (silylorganyl) polysulphanes. Both the'085 and '275 patents describe anhydrous techniques involving the directreaction of a haloalkoxysilane with a polysulphide.

U.S. Pat. No. 6,066,752 teaches a process for producingsulfur-containing organosilicon compounds by reacting sulfur, an alkalimetal, and a halogenalkoyxsilane in the absence of a solvent or in thepresence of an aprotic solvent.

Most recently, U.S. Pat. No. 6,140,524 describes a method for preparingshort chain polysulfide silane mixtures of the formula(RO)₃SiC₃H₆S_(n)C₃H₆Si(RO)₃ having a distribution where n falls in therange of 2.2≦n≦2.8. The '524 method reacts metal polysulfides, typicallyNa₂S_(n) with a halogenopropyltrialkoxysilane having the formula(RO)₃SiC₃H₆X wherein X is a halogen, in alcohol solvent.

Alternative processes for the preparation of sulfur-containingorganosilanes have been taught in the art based on the use of phasetransfer catalysis techniques. Phase transfer catalysis techniquesovercome many of the practical problems associated with theaforementioned prior art processes for producing sulfur-containingorganosilicon compounds. Many of these problems are related to the useof solvents. In particular, the use of ethyl alcohol can be problematicbecause of its low flash point. Additionally, it is difficult to obtainand maintain anhydrous conditions necessary in many of theaforementioned prior art processes on an industrial scale.

Phase transfer catalysis techniques for producing sulfur-containingorganosilicon compounds are taught for example in U.S. Pat. Nos.5,405,985, 5,663,396, 5,468,893, and 5,583,245. While these patentsteach new processes for the preparation of sulfur containingorganosilicon compounds using phase transfer catalysis, there stillexist many practical problems with the use of phase transfer techniquesat an industrial scale. For example, there is a need to control thereactivity of the phase transfer catalyst in the preparation ofsulfur-containing organosilanes so as to provide efficient, yet safereactions, that can be performed on an industrial scale. Furthermore,there is a need to improve the final product stability, appearance andpurity. In particular, the phase transfer catalysis process of the priorart results in final product compositions containing high quantities ofun-reacted sulfur species. These un-reacted sulfur species canprecipitate in stored products with time causing changes in productsulfide distribution.

The need to improve product quality is of particular importance when analkali metal or ammonium hydrogen sulfide is used as a starting materialin phase transfer catalysis techniques. In these reactions, dangerousand odorous hydrogen sulfide is produced in side reactions. Productcompositions containing even minor amounts of hydrogen sulfide detertheir use in large scale industrial processes.

Yet another problem associated with the use of phase transfer catalysistechniques for producing sulfur containing organosilicon compounds isgelation, caused by the hydrolysis of the alkoxy groups on theorganosilicon compound, or starting silane reactant, with the aqueousphase reactants.

It is therefore an object of the present invention to provide animproved process for the production of sulfur containing organosiliconcompounds based on phase transfer catalysis techniques.

It is a further object of the present invention to provide a process forproducing sulfur containing organosilicon compounds based on phasetransfer catalysis techniques that result in a final product compositionof greater stability, purity, and appearance.

It is yet a further object of the present invention to provide a processfor producing sulfur containing organosilicon compounds based on phasetransfer techniques using a hydrosulfide compound that minimizes oreliminates hydrogen sulfide as a side product.

It is still yet a further object of the present invention to provide aprocess for producing sulfur containing organosilicon compounds based onphase transfer techniques where gelation of starting materials orresulting products is minimized or eliminated.

SUMMARY OF THE INVENTION

The present invention provides a process for the production of sulfurcontaining organosilicon compounds by a buffered phase transfercatalysis techniques. Sulfur containing organosilicon compounds areprepared by the process of the present invention by reacting ammoniumhydrosulfide or an alkali metal hydrosulfide, and optionally sulfur,with a silane compound having the formula

(RO)_(3−m)R_(m)Si—Alk—X

where X is Cl, Br or I,

in the presence of a phase transfer catalyst and an aqueous phasecontaining a buffer.

The improvement of the present invention is characterized by adding abuffer to the aqueous phase. The present invention also provides animproved process for the production of sulfur containing organosiliconcompounds by controlling the pH of the aqueous phase.

The present invention also encompasses the organosilicon compoundsproduced by the improved process.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a process for the production of organosiliconcompounds of the formula:

(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m)

where

R is independently a monovalent hydrocarbon of 1 to 12 carbon

atoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms;

m is an integer of 0 to 2, n is a number from 1 to 8;

comprising reacting:

(A) a sulfide compound having the formula M₂S_(n) or MHS,

where H is hydrogen, M is ammonium or an alkali metal,

n is as defined above, with

(B) a silane compound of the formula;

(RO)_(3−m)R_(m)Si—Alk—X

where X is Cl, Br or I, and m is the same as above, and optionally,

(C) sulfur

in the presence of a phase transfer catalyst and an aqueous phasecontaining a buffer.

Examples of sulfur containing organosilicon compounds which may beprepared in accordance with the present invention are described in U.S.Pat. Nos. 5,405,985, 5,663,396, 5,468,893, and 5,583,245, which arehereby incorporated by reference. The preferred sulfur containingorganosilicon compounds which are prepared in accordance with thepresent invention are the 3,3′-bis(trialkoxysilylpropyl) polysulfides.The most preferred compounds are 3,3′-bis(triethoxysilylpropyl)disulfide and 3,3′-bis(triethoxysilylpropyl) tetrasulfide.

Sulfide compounds of the formula M₂S_(n) or MHS can be used as component(A) in the reaction step of the process of the present invention, whereM represents an alkali metal or ammonium group and H representshydrogen. Representative alkali metals include lithium, potassium,sodium, rubidium, or cesium. Preferably M is sodium. Generally, MHScompounds are used preferentially when the average value of n in theresulting product formula,(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m) is desired to be 2.Examples of the MHS compound include NaHS, KHS, and NH₄HS. When thesulfide compound is an MHS compound, NaHS is preferred. Specificexamples of the NaHS compound include NaHS flakes (containing 71.5-74.5%NaHS) and NaHS liquors (containing 45-60% NaHS) from PPG of Pittsburgh,Pa. M₂S_(n) compounds are used preferentially when the average value ofn in the resulting product formula,(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m) is desired to be 4.Specific examples of compounds of M₂S_(n) include Na₂S, K₂S, Cs₂S,(NH₄)₂S, Na₂S₂, Na₂S₃, Na₂S₄, Na₂S₆, K₂S₂ K₂S₃, K₂S₄, K₂S₆, and(NH₄)₂S₂. Preferably the sulfide compound is Na₂S. A particularpreferred sulfide compound is sodium sulfide flakes (containing 60-63%Na₂S) from PPG of Pittsburgh, Pa.

Component (B) in the reaction step of the process of the presentinvention is a silane compound of the formula;

(RO)_(3−m)R_(m)Si—Alk—X

R can independently be any hydrocarbon group containing 1 to 12 carbonatoms. Thus, examples of R can include methyl, ethyl, propyl, butyl,isobutyl, cyclohexyl, or phenyl. Preferably, R is a methyl or ethylgroup. In the formula (RO)_(3−m)R_(m)Si—Alk—X, m is an integer and canhave a value from 0 to 2. Preferably, m is equal to 0. Alk is a divalenthydrocarbon group containing 1 to 18 carbons. Alk can be for example;ethylene, propylene, butylene, or isobutylene. Preferably Alk contains 2to 4 carbons, and most preferable Alk is a propylene group. X is ahalogen atom selected from chlorine, bromine, or iodine. Preferably X ischlorine. Examples of silane compounds that may be used in the presentinvention include chloropropyl triethoxy silane, chloropropyl trimethoxysilane, chloroethyl triethoxy silane, chlorobutyl triethoxy silane,chloroisobutylmethyl diethoxy silane, chloroisobutylmethyl dimethoxysilane, chloropropyldimethyl ethoxy silane. Preferably, the silanecompound of the present invention is chloropropyl triethoxy silane(CPTES).

Sulfur can also be added to the reaction step on the process of thepresent invention as an optional component, (C). The sulfur used in thereaction of the present invention is elemental sulfur. The type and formare not critical and can include those commonly used. An example of asuitable sulfur material is 100 mesh refined sulfur powder from Aldrich,Milwaukee Wis.

The amount of sulfur and sulfide compound used in the process of thepresent invention can vary, but preferably the molar ratio of S/M₂S_(n)or S/MHS ranges from 0.3 to 5. The molar ratio of sulfur/sulfidecompound can be used to affect the final product distribution, that isthe average value of n in the formula,(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m). When the averagevalue of n is desired to be 4 in the product formula,(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m), the preferred rangefor the ratio of sulfur/sulfide compound is from 2.7 to 3.2. When theaverage value of n is desired to be 2 in the product formula,(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m), the preferred rangefor the ratio of sulfur/sulfide compound is from 0.8 to 1.2.

The silane compound, (RO)_(3−m)R_(m)Si—Alk—X, can be reacted in thepresence of or absence of a solvent with the sulfide compound, oralternatively with the sulfide compound and sulfur in combination, asdescribed above. The silane compound can also be dispersed in an organicsolvent to form an organic phase. Representative examples of organicsolvents include toluene, xylene, benzene, heptane, octane, nonane,decane, chlorobenzene and the like. When an organic solvent is used, thepreferred organic solvent is toluene.

When conducting the reaction of the present invention, preferably thesilane compound is reacted directly with the sulfide compound and sulfurin combination as described above.

The amount of the silane compound (RO)_(3−m)R_(m)Si—Alk—X used in theprocess of the present invention can vary. An example of a suitablemolar range includes from 1/10 to 10/1 based on the amount of sulfidecompound used. When the average value of n is desired to be 4 in theproduct formula, (RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m), thesilane compound (RO)_(3−m)R_(m)Si—Alk—X is used from 2.0 to 2.10 inmolar excess of the M₂S_(n) sulfide compound, with a range of 2.01 to2.06 being the most preferable. When the average value of n is desiredto be 2 in the product formula,(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m), the silane compound(RO)_(3−m)R_(m)Si—Alk—X is used from 1.8 to 2.10 in molar excess of theMHS sulfide compound, with a range of 1.9 to 2.0 being the mostpreferable.

The phase transfer catalysts operable in the present invention are thequaternary onium cations. Preferred examples of the quaternary oniumcations as phase transfer catalysts are described in U.S. Pat. No.5,405,985, which is hereby incorporated by reference. Preferably, thequaternary onium cation is tetrabutyl ammonium bromide or tetrabutylammonium chloride. The most preferred quaternary onium salt istetrabutyl ammonium bromide. A particularly preferred quaternary oniumsalt is tetrabutyl ammonium bromide (99%) from Aldrich Chemical ofMilwaukee, Wis.

The amount of the phase transfer catalyst used in the process may vary.Preferably the amount of phase transfer catalyst is from 0.1 to 10weight %, and most preferably from 0.5 to 2 weight % based on the amountof silane compound used.

The phase transfer catalyst may be added to the reaction at any time.Preferably, the phase transfer catalyst is added to the aqueous phaseprior the reaction step of the process of the present invention.

The reaction of the present invention is conducted in the presence of anaqueous phase containing a buffer. The buffer can be a single compoundsuch as an alkali metal salt of a phosphate, a hydrogen phosphate, adihydrogen phosphate, a carbonate, a hydrogen carbonate, or a borate, orcombinations thereof. Examples of buffers include; Na₃PO₄, Na₂HPO₄,NaH₂PO₄, Na₂CO₃, NaHCO₃, and NaB₄O₇. Preferably, the buffer is selectedfrom Na₃PO₄, Na₂CO₃, or K₂CO₃ When the average value of n is desired tobe 4 in the product formula,(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m), the preferred bufferis Na₃PO₄. When the average value of n is desired to be 2 in the productformula, (RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m), thepreferred buffer is Na₂CO₃ or K₂CO₃.

The amount of the buffer added to the aqueous phase can vary, butgenerally is added in molar amounts equal to or greater than the numberof moles of M₂S_(n) or MHS.

In a preferred embodiment of the present invention, the sulfidecompound, the phase transfer catalyst, the buffer, water, and optionallysulfur, are mixed together to form an intermediate reaction product.This reaction can be conducted at a variety of temperatures, butgenerally in the range of 40-100° C. Preferably, the reaction isconducted at a temperature ranging from 65-95° C. Generally, the firststep can be conducted at various pressures, but preferably the firststep reaction is conducted at atmospheric pressure. The time needed forthe reaction of the first step to occur is not critical, but generallyranges from 5 to 30 minutes. The intermediate reaction product is thenreacted with the silane compound, (RO)_(3−m)R_(m)Si—Alk—X. The timeneeded for the reaction of the intermediate reaction product and silanecompound to occur is not critical, but generally ranges from 5 minutesto 6 hours.

The amount of water used to create the aqueous phase or intermediatereaction product can vary, but is preferably based on the amount of thesilane compound (III) used in the process. Water can be added directly,or indirectly, as some water may already be present in small amounts inother starting materials. For purposes of the present invention, it ispreferable to calculate the total amount of water present, that is,accounting for all water added either directly or indirectly.Preferably, the total amount of water used to create the aqueous phaseor the intermediate reaction product is 1 to 100 weight % of the silanecompound used, with a range of 2.5 to 70 weight % being more preferred.Most preferred is a range of 20 to 40 weight % of water used for theintermediate reaction product based on the amount of silane compoundused. Although not to be limited to any theory, the present inventorsbelieve the addition of a buffer to the aqueous phase in the process toprepare sulfur containing organosilicon compounds using phase transfercatalysis helps to control the pH of the reaction medium, therebyaffecting product formation and minimizing side reactions, such as theproduction of hydrogen sulfide; or the production of mercaptan silanehaving the general formula (RO)_(3−m)R_(m)Si—Alk—SH. Thus, as a secondembodiment of the present invention, sulfur containing organosiliconcompounds can be produced in the reaction described above by controllingthe pH. The pH of the aqueous phase used in the reaction of the presentinvention can be controlled by the addition of a buffer, as describedabove, or alternatively, by the addition of any acidic or basiccompounds at such a rate and concentration so as to maintain a pH duringthe reaction in the range of 7 to 14. The present inventors have alsofound that pH can have an influence on the product distribution, thatis, the value of n in the product formula(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m). When the averagevalue of n is desired to be 2 in the product formula,(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m), the preferred pHrange is from 8 to 10. When the average value of n is desired to be 4 inthe product formula, (RO)_(3-m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m) (OR)_(3-m),the preferred pH range is from 11 to 14.

The silane compound is added to the aqueous phase, or to theintermediate reaction product, as described above, at such a rate so asto control the exothermic reaction, and maintain a temperature in therange of 40 to 110° C. Preferably the reaction temperature is maintainedat 60 to 95° C. The reaction progress can be monitored by theconsumption of the silane compound starting material. The amount ofcatalyst and reaction temperature affects the reaction time necessaryfor completion.

At the end of the reaction, a product mixture is produced containing anorganic phase, an aqueous phase, and possibly precipitated solidmaterials that can include salts such as NaCl, Na₂HPO₄, or NaHCO₃ (oranalogous potassium salts) formed during the reaction. The organic phasecontains the organosilane compound.

The present invention also encompasses processing steps to enhance theseparation of the organosiloxane compound from the product mixture. Thisseparation can be the phase separation of the organic and aqueous phase,resulting directly from the reaction of components (A), (B), andoptional (C), as described above. Alternatively, if precipitated saltsare formed during the reaction, the salts can be separated first by afiltering process or decanting method prior to the phase separation.Preferably, water or a dilute acidic solution is added to the productmixture prior to separation. The addition of water or a dilute acidicsolution can enhance the phase separation by dissolving some or all ofthe precipitated salts. The amount of water or dilute acidic solutionthat is added during this step can vary from 10 to 50 weight % based onthe weight of the amount of silane compound used, preferably, the amountof water or dilute acidic solution added is from 20 to 40 weight % basedon the amount of the silane compound used, and most preferably from 25weight % to 35 weight %. When a dilute acidic solution is used, it canbe any of the common acids, for example HCl, HNO₃, H₂SO₄, or the like,having a normal (N) concentration of 0.000001 to 5, preferably 0.01to 1. The dilute acidic solution can also be prepared by the addition ofa chlorosilane to water. Examples of chlorosilanes that can be used tocreate the dilute acidic solution include trichlorosilane,trichloromethylsilane, dimethyldichlorosilane, dimethylchlorosilane,trimethylchlorosilane. Preferably, 0.5 to 10 weight % chlorosilane canbe used to prepare the dilute acidic solution, with 1 to 5 weight %being the most preferred. When a chlorosilane is used to create thedilute acidic solution, the chlorosilane is preferablytrimethylchlorosilane.

Following the addition of water or a dilute acidic solution to theproduct mixture, the organosilicon compound is isolated from the productmixture by phase separating the organic phase and aqueous phase. Theorganic phase containing the organosilicon compound can be furthersubjected to a drying step. One example of the drying step can be totreat the organic phase under vacuum to remove any volatile organicmaterials present along with any residual water that may be present.This drying step can involve, for example, heating the organic phase toa temperature of 20 to 160° C. under a reduced pressure of 5 to 35 mm Hg(0.67 to 4.65 kPa), preferably the conditions are 90 to 120° C. at 5 to25 mm Hg (0.67 to 3.33 kPa). Alternatively, the drying step of theorganic phase can involve the use of a thin film stripper to removevolatile organics materials and residual water content in the organicphase. Yet another technique for the drying step of the organic phasecan be to contact the organic phase containing the organosiliconcompound with a desiccant material. The desiccant material can be anysolid material known in the art to remove trace quantities of water inorganic phases. These include known ionic hygroscopic materials likesodium sulfate, magnesium sulfate, and the like, or silicate basedmaterials such as zeolites, silica, aluminasilicates, and the like. Thepreferred desiccant material is either sodium sulfate or magnesiumsulfate, with sodium sulfate being the most preferred.

The dried organic phase can be subjected to additional steps accordingto the present invention that result in further improvements of theorganosilicon compound final purity and appearance. The organic phasecontaining the organosilicon compound can be cooled to a temperaturebelow 15° C. This cooling step results in the precipitation ofun-reacted sulfur and sulfur compounds. Preferably, the organic phasecontaining the organosilicon compound is cooled to a temperature in therange of −20 to 30° C., and most preferably to a temperature in therange of −15 and 15° C. The precipitated un-reacted sulfur and sulfurcompounds can then be separated, for example by filtration, from theorganic phase containing the organosilicon compound. The presentinventors have found that removing un-reacted sulfur and sulfurcompounds minimizes or eliminates further precipitation of sulfur andun-reacted sulfur compounds with time. As a result, the long-termstorage stability of the organosilicon compound is enhanced by producinga composition that does not change with time or result in a productcomposition containing solid precipitates.

The following examples are provided to illustrate the present invention.These examples are not intended to limit the scope of the claims herein.

EXAMPLES

The distribution of the various sulfur containing organosiliconcompounds were analyzed by high-pressure liquid chromatography (HPLC).Typical run conditions for HPLC analysis were as follows: 8-9 drops ofthe reaction sample were diluted in 8.5 g of cyclohexane, which was thenfiltered through a 0.2 μm PTFE membrane (e.g. PURADISC™ 25TF ofWhatman®) into a vial, a 10 μl sample of the filtrate was injected viaan autosampler into a HPLC system (e.g. Hewlett-Packard 1050). Thesample was fractionated on a Lichrosorp RP18 column (e.g. AlltechAssoc., Inc; 250 mm×4.6 mm, 10 μm) using a mixture of 96% acetonitrileand 4% tetrahydrofurane (vol/vol) as mobile phase. The fractions wereinvestigated via UV-absorption detector using 254 nm as the appropriateexcitation wavelength. Different UV-sensitivities of every singlesulfide species were averaged by division of the respective peak areathrough specific, empirically evaluated, response factors* (RF) listedbelow that reflect the hyperchromy with every sulfur atom in the chainand elemental sulfur.

As reported by H.-D. Luginsland, “Reactivity of the Sulfur Functions ofthe Disulfane Silane TESPD and the Tetrasulfane Silane TESPT”; RubberDivision, American Chemical Society; Chicago, Ill., Apr. 13-16, 1999.

HPLC Response Factors

S2 S3 S4 S5 S6 S7 S8 S9 S10 S_(elem.) 1.0 3.52 6.39 9.78 13.04 17.3920.87 26.08 31.30 37.26

Comparative Example

A 100-ml-flask, equipped with magnetic stir bar and internal thermometerwas loaded at 76 degrees Celsius with 6.75 g of disodium sulfide (59.75%Na₂S, 0.26% NaHS), and 2.08 g of elemental sulfur. Then, 6.25 g of waterwere added and the mixture stirred until all solids were dissolved.Then, 1.00 g of a 25% aqueous catalyst solution (0.25 g of tetrabutylammonium bromide in 0.75 g of water) was added. Then 6.03 g ofchloropropyltriethoxysilane were added via syringe in 1 mL portions.Within 20 minutes, the reaction temperature increased to 80 degreesCelsius and the mixture immediately solidified to form an orange-browngel. Further addition of chloropropyltriethoxysilane resulted in theformation of a white resin on top of the gel.

Example 1

A 100-ml-flask, equipped with magnetic stir bar, condenser and internalthermometer, was loaded at 78 degrees Celsius with 4.01 g of flakedsodium hydrogen sulfide (2.08% Na₂S, 71.10% NaHS), 1.66 g of elementalsulfur and 7.37 g of disodium sulfate. 12.50 g of water were added andthe mixture was stirred until all solids were dissolved. Strongformation of dihydrogen sulfide gas was observed. 1.00 g of a 25%aqueous catalyst solution (0.25 g of tetrabutyl ammonium bromide in 0.75g of water) was added. Then 23.75 g of chloropropyltriethoxysilane wereadded via syringe within 40 minutes in portions of 2 ml. The reactiontemperature increased to 79 degrees Celsius. After the decrease of theexotherm, the mixture was stirred at a temperature of 78 degreesCelsius, and the reaction progress was followed by quantitative gaschromatography analysis until chloropropyltriethoxysilane had reached astable level after 2.75 hours. The reaction mixture was cooled to roomtemperature and 20.18 g of a clear and nearly colorless liquid werecollected via pipette from top of the aqueous phase. High pressureliquid chromatography analysis showed an average sulfur rank of 3.11.Quantitative gas chromatography analysis showed 36.45% un-reactedchloropropyltriethoxysilane.

Example 2

A 100-ml-flask, equipped with magnetic stir bar, condenser and internalthermometer, was loaded at 76 degrees Celsius with 4.01 g of flakedsodium hydrogen sulfide (2.08% Na₂S, 71.10% NaHS), 1.66 g of elementalsulfur and 10.45 g of disodium tetraborate (Na₂B₄O₇). 12.50 g of waterwere added and the mixture was stirred until all solids were dissolved.Slight formation of dihydrogen sulfide gas was observed. 1.00 g of a 25%aqueous catalyst solution (0.25 g of tetrabutyl ammonium bromide in 0.75g of water) was added. Then 23.75 g of chloropropyltriethoxysilane wereadded via syringe within 44 minutes in portions of 2 ml every fourminutes. The reaction temperature increased to 78 degrees Celsius. Afterthe decrease of the exotherm, the mixture was stirred at a temperatureof 76 degrees Celsius, and the reaction progress was followed byquantitative gas chromatography analysis untilchloropropyltriethoxysilane had reached a stable ratio level after 3hours. The reaction mixture was cooled to room temperature and 22.88 gof a clear and nearly colorless liquid were collected via pipette fromtop of the aqueous phase. High pressure liquid chromatography analysisshowed an average sulfur rank of 2.53. Quantitative gas chromatographyanalysis showed 21.03% unreactedchloropropyltriethoxysilane.

Example 3

A 100-ml-flask, equipped with magnetic stir bar, condenser and internalthermometer, was loaded at 78 degrees Celsius with 4.01 g of flakedsodium hydrogen sulfide (2.08% Na₂S, 71.10% NaHS), 1.66 g of elementalsulfur and 5.51 g of disodium carbonate. Then, 18.75 g of water wereadded and the mixture was stirred until all solids were dissolved. Then,1.00 g of a 25% aqueous catalyst solution (0.25 g of tetrabutyl ammoniumbromide in 0.75 g of water) was added. Then 23.75 g ofchloropropyltriethoxysilane were added via syringe within 33 minutes inportions of 2 ml every three minutes. The reaction temperature increasedto 80 degrees Celsius. After the decrease of the exotherm, the mixturewas stirred at a temperature of 79 degrees Celsius, and the reactionprogress was followed by quantitative gas chromatography analysis untilchloropropyltriethoxysilane has reached a stabile ratio level after 3.25hours. The reaction mixture was cooled down to 50 degrees Celsius and9.73 g of water were added. The mixture was stirred until all formedsalts were dissolved. The mixture was cooled to 30 degrees Celsius and22.64 g of a clear and nearly colorless liquid were collected viapipette from top of the aqueous phase. High pressure liquidchromatography analysis showed an average sulfur rank of 2.16.Quantitative gas chromatography analysis showed 3.46% un-reactedchloropropyltriethoxysilane.

Example 4

A 100-ml-flask, equipped with magnetic stir bar, condenser and internalthermometer, was loaded at 74 degrees Celsius with 4.01 g of flakedsodium hydrogen sulfide (2.08% Na₂S, 71.10% NaHS), 1.66 g of elementalsulfur and 8.51 g of trisodium phosphate. Then, 12.50 g of water wereadded and the mixture was stirred until all solids were dissolved. Then,1.00 g of a 25% aqueous catalyst solution (0.25 g of tetrabutyl ammoniumbromide in 0.75 g of water) was added. Then 24.00 g ofchloropropyltriethoxysilane were added via syringe within 33 minutes inportions of 2 ml every three minutes. The reaction temperature increasedto 78 degrees Celsius. After the decrease of the exotherm, the mixturewas stirred at a temperature of 76 degrees Celsius, and the reactionprogress was followed by quantitative gas chromatography analysis untilchloropropyltriethoxysilane had reached a stable ratio level after 2.75hours. The reaction mixture was cooled down to room temperature and21.14 g of a clear and nearly colorless liquid were collected viapipette from top of the aqueous phase. High pressure liquidchromatography analysis showed an average sulfur rank of 2.12.Quantitative gas chromatography analysis showed 1.66% un-reactedchloropropyltriethoxysilane.

Example 5

A 1-1-reactor, equipped with mechanical stirrer, 1 baffle, condenser,dropping funnel, and internal thermometer, was loaded at 74 degreesCelsius with 72.18 g of flaked sodium hydrogen sulfide (2.08% Na₂S,71.10% NaHS), 29.94 g of elemental sulfur and 153.00 g of trisodiumphosphate. Then, 225 g of water were added and the mixture wasvigorously stirred until all solids were dissolved. Then, 18.00 g of a25% aqueous catalyst solution (4.50 g of tetrabutyl ammonium bromide in13.50 g of water) were added. Then 427.50 g ofchloropropyltriethoxysilane were added within 70 minutes and thereaction temperature raised to 82 degrees Celsius. After the decrease ofthe exotherm, the mixture was stirred at a temperature of 79 degreesCelsius, and the reaction progress was followed by gas chromatographyanalysis until chloropropyltriethoxysilane had reached a stable ratiolevel after 2.75 hours. The mixture was cooled to 50 degrees Celsiuswhen 150 g of water were added. The mixture was further cooled to 30degrees Celsius and another 25.0 g of water were added. The mixture wasstirred until all formed salts were dissolved. Then, 664.65 g of aclear, colorless aqueous phase were drained off. The remaining organicphase was also drained off and without further purification 419.81 g ofa clear, light yellow liquid were received. High pressure liquidchromatography analysis showed an average sulfur rank of 2.12.Quantitative gas chromatography analysis showed 0.73% un-reactedchloropropyltriethoxysilane.

Example 6

A 100-ml-flask, equipped with magnetic stir bar, condenser and internalthermometer, was loaded at 76 degrees Celsius with 4.01 g of flakedsodium hydrogen sulfide (2.08% Na₂S, 71.10% NaHS), 4.99 g of elementalsulfur and 8.51 g of trisodium phosphate. Then, 12.50 g of water wereadded and the mixture was stirred until all solids were dissolved. Then,1.00 g of a 25% aqueous catalyst solution (0.25 g of tetrabutyl ammoniumbromide in 0.75 g of water) was added. Then 24.00 g ofchloropropyltriethoxysilane were added via syringe within 36 minutes inportions of 2 ml every three minutes. The reaction temperature increasedto 79 degrees Celsius. After the decrease of the exotherm, the mixturewas stirred at a temperature of 78 degrees Celsius, and the reactionprogress was followed by quantitative gas chromatography analysis untilchloropropyltriethoxysilane has reached a stable ratio level after 4hours. The reaction mixture was cooled to 50 degrees C., when 9.72 g ofwater were added to dissolve the sodium chloride. The mixture was cooledto room temperature and 24.38 g of a orange-brown liquid were collectedvia pipette from top of the aqueous phase. High pressure liquidchromatography analysis showed an average sulfur rank of 3.86.

Example 7

A 1-1reactor, equipped with mechanical stirrer, 1 baffle, condenser,dropping funnel, and internal thermometer, was loaded at 76 degreesCelsius with 450.00 g of water. Then, 153.13 g of trisodium phosphateand 132.63 g of disodium hydrogen phosphate were added in portions. Themixture was vigorously stirred until all salts were dissolved. Then,38.01 g of an aqueous solution of sodium hydrogen sulfide (0.24% Na₂S,45.77% NaHS) were added. Then, 9.98 g of elemental sulfur were added andthe mixture was stirred until a clear, dark amber solution was formed.4.00 g of a 25% aqueous catalyst solution (1.00 g of tetrabutyl ammoniumbromide in 3.00 g of water) were added. Then 150.00 g ofchloropropyltriethoxysilane were added within 15 minutes and thereaction temperature increased to 79.5 degrees Celsius. Another 2.00 gof the 25% aqueous catalyst solution (1.00 g of tetrabutyl ammoniumbromide in 3.00 g of water) were added. After the decrease of theexotherm, the mixture was stirred at a temperature of 76 degreesCelsius, and the reaction progress was followed by gas chromatographyanalysis until chloropropyltriethoxysilane has reached a stable ratiolevel after 2.5 hours. Then, 787.77 g of clear colorless aqueous phasewere drained off. The remaining organic phase was cooled down to 15degrees Celsius, drained off (132.01 g raw material) and filtered in aBüchner funnel through Paper (e.g. Whatman® 1) to yield 127.18 g of aclear, light yellow liquid. High pressure liquid chromatography analysisshowed an average sulfur rank of 2.04. Quantitative gas chromatographyanalysis showed 0.65% un-reacted chloropropyltriethoxkysilane.

Example 8

A 1-1-reactor, equipped with mechanical stirrer, 1 baffle, condenser,dropping funnel, and internal thermometer, was loaded at 76 degreesCelsius with 450.00 g of water. 102.12 g of trisodium phosphate and176.84 g of disodium hydrogen phosphate were added in portions. Themixture was vigorously stirred until all salts were dissolved. Then,38.01 g of an aqueous solution of sodium hydrogen sulfide (0.24% Na₂S,45.77% NaHS) were added. Then, 9.98 g of elemental sulfur were added andthe mixture was stirred until a clear, dark amber solution was formed.4.00 g of a 25% aqueous catalyst solution (1.00 g of tetrabutyl ammoniumbromide in 3.00 g of water) were added. Then 150.00 g ofchloropropyltriethoxysilane were added within 15 minutes and thereaction temperature increased to 79.0 degrees Celsius. Another 2.00 gof the 25% aqueous catalyst solution (1.00 g of tetrabutyl ammoniumbromide in 3.00 g of water) were added. After the decrease of theexotherm, the mixture was stirred at a temperature of 76 degreesCelsius, and the reaction progress was followed by gas chromatographyanalysis until chloropropyltriethoxysilane had reached a stable ratiolevel after 3 hours. Then, 771.09 g of clear colorless aqueous phasewere drained off. The remaining organic phase was cooled to 15 degreesCelsius, drained off (133.82 g raw material) and filtered in a Büchnerfunnel through Paper (e.g. Whatman® 1) to yield 130.08 g of a clear,light yellow liquid. High pressure liquid chromatography analysis showedan average sulfur rank of 2.05. Quantitative gas chromatography analysisshowed 1.07% un-reacted chloropropyltriethoxysilane.

Example 9

A 1-1-reactor, equipped with mechanical stirrer, 1 baffle, condenser,dropping funnel, and internal thermometer, was loaded at 76 degreesCelsius with 450.00 g of water. 51.06 g of trisodium phosphate and221.05 g of disodium hydrogen phosphate were added in portions. Themixture was vigorously stirred until all salts were dissolved. Then,38.01 g of an aqueous solution of sodium hydrogen sulfide (0.24% Na₂S,45.77% NaHS) were added. Then, 9.98 g of elemental sulfur were added andthe mixture was stirred until a clear, dark amber solution was formed.Then, 4.00 g of a 25% aqueous catalyst solution (1.00 g of tetrabutylammonium bromide in 3.00 g of water) were added. Then 150.00 g ofchloropropyltriethoxysilane were added within 15 minutes and thereaction temperature increased to 79.0 degrees Celsius. Another 2.00 gof the 25% aqueous catalyst solution (1.00 g of tetrabutyl ammoniumbromide in 3.00 g of water) were added. After the decrease of theexotherm, the mixture was stirred at a temperature of 76 degreesCelsius, and the reaction progress was followed by gas chromatographyanalysis until chloropropyltriethoxysilane had reached a stable ratiolevel after 3.5 hours. Then 762.30 g of a clear colorless aqueous phasewere drained off The remaining organic phase was cooled to 15 degreesCelsius, drained off (143.04 g raw material) and filtered in a Büchnerfunnel through Paper (e.g. Whatman® 1) to yield 141.18 g of a clear,light yellow liquid. High pressure liquid chromatography analysis showedan average sulfur rank of 2.09. Quantitative gas chromatography analysisshowed 2.77% un-reacted chloropropyltriethoxysilane.

Example 10

A 1-1-reactor, equipped with mechanical stirrer, 1 baffle, condenser,dropping funnel and internal thermometer, was loaded at 76 degreesCelsius with 450.00 g of water. Then, 265.26 g of disodium hydrogenphosphate were added in portions. The mixture was vigorously stirreduntil all salts were dissolved. Then, 38.01 g of an aqueous solution ofsodium hydrogen sulfide (0.24% Na₂S, 45.77% NaHS) were added. Then, 9.98g of elemental sulfur were added and the mixture was stirred until aclear, dark amber solution was formed. Then, 4.00 g of a 25% aqueouscatalyst solution (1.00 g of tetrabutyl ammonium bromide in 3.00 g ofwater) were added. Then 150.00 g of chloropropyltriethoxysilane wereadded within 15 minutes and the reaction temperature raised to 79.0degrees Celsius. Another 2.00 g of the 25% aqueous catalyst solution(1.00 g of tetrabutyl ammonium bromide in 3.00 g of water) were added.After the decrease of the exotherm, the mixture was stirred at atemperature of 76 degrees Celsius, and the reaction progress wasfollowed by gas chromatography analysis untilchloropropyltriethoxysilane had reached a stable ratio level after 4.5hours. Then, 756.55 g of a clear colorless aqueous phase were drainedoff. The remaining organic phase was cooled to 15 degrees Celsius,drained off (143.49 g raw material) and filtered in a is Büchner funnelthrough Paper (e.g. Whatman® 1) to yield 140.48 g of a clear, lightyellow liquid. High pressure liquid chromatography analysis showed anaverage sulfur rank of 2.19. Quantitative gas chromatography analysisshowed 11.92% un-reacted chloropropyltriethoxysilane.

Example 11

A jacketed 1.5 L reactor equipped with a mechanical stirrer, 1 baffle,and an internal thermocouple was charged at room temperature with 419.81g of water. Then, 151.33 g solid K₂CO₃, 134.85 g aqueous NaSH solution(45.85 wt % NaSH) and 34.96 g sulfur powder were charged to the reactorwith mixing. The reactor contents were then heated to 70° C., afterholding at 70° C. for 5 minutes, 21.01 g of a 25 wt % aqueoustetrabutylammoniumbromide (TBAB) solution was charged to the reactor andallowed to mix for 10-15 minutes. Then, 500.02 g. ofchloropropyltriethoxysilane (CPTES) was charged to the reactor dropwisevia an addition funnel. The CPTES addition rate was limited by thecooling jacket capability and a desire to maintain the reactortemperature below 85 C. After the addition of CPTES, the reactor washeld at 75° C. for 2 to 3.5 hours until the reaction was determined tobe complete, as determined by no further conversion of CPTES as measuredby gas chromatographic analysis of the organic phase. After the reactionwas complete, the reactor was cooled to 50° C. and water was added tothe reactor to dissolve the salts present in the reactor. Agitation wasthen stopped and the reactor contents allowed to phase separate. Thelower aqueous phase was then drained off, leaving behind 458.9 g. ofproduct. Un-reacted CPTES and other low boiling impurities (2.50 wt % ofthe crude product) were removed by vacuum stripping leaving behind afinal product, ((EtO)₃SiCH₂CH₂CH₂)₂S_(x), with x=2.12.

Example 12

A jacketed 1.5 L reactor equipped with a mechanical stirrer, 1 baffle,and an internal thermocouple was charged at room temperature with 50.56g of water. Then, 317.8 g of an 47.6 wt % aqueous K₂CO₃ solution, 135.09g aqueous NaSH solution (45.56 wt % NaSH) and 37.04 g sulfur flakes werecharged to the reactor with mixing. The reactor contents were thenheated to 70° C. After holding at 70° C. for 5 minutes, 20.99 g of a 25wt % aqueous tetrabutylammoniumbromide (TBAB) solution was charged tothe reactor and allowed to mix for 10-15 minutes. Then, 500.02 g. ofchloropropyltriethoxysilane (CPTES) was charged to the reactor dropwisevia an addition funnel. The CPTES addition rate was limited by thecooling jacket capability and a desire to maintain the reactortemperature below 85° C. After the addition of CPTES, the reactor washeld at 75° C. for 2 to 3.5 hours until the reaction was determined tobe complete, as determined by no further conversion of CPTES, asmeasured by gas chromatographic analysis of the organic phase. After thereaction was complete, the reactor was cooled to 50° C. and water wasadded to the reactor to dissolve the salts present in the reactor.Agitation was then stopped and the reactor contents allowed to phaseseparate. The lower aqueous phase was then drained off, leaving behind479.1 g. of product. Unreacted CPTES and low boiling impurities (1.77 wt% of the crude product) were removed by vacuum stripping leaving behinda final product, ((EtO)₃SiCH₂CH₂CH₂)₂S_(x), with x=2.16.

We claim:
 1. A process for the production of organosilicon compounds ofthe formula: (RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m) where Ris independently a monovalent hydrocarbon of 1 to 12 carbon atoms; Alkis a divalent hydrocarbon of 1 to 18 carbon atoms; m is an integer of 0to 2, n is a number from 1 to 8; comprising reacting: (A) a sulfidecompound having the formula M₂S_(n) or MHS, where H is hydrogen, M isammonium or an alkali metal, n is as defined above, with (B) a silanecompound of the formula; (RO)_(3−m)R_(m)Si—Alk—X where X is Cl, Br or I,and m is the same as above, and optionally, (C) sulfur in the presenceof a phase transfer catalyst and an aqueous phase containing a buffer.2. The process of claim 1 wherein the buffer is an alkali metal salt ofa phosphate, a hydrogen phosphate, a dihydrogen phosphate, a carbonate,a hydrogen carbonate, or a borate.
 3. The process of claim 1 wherein thebuffer is selected from Na₃PO₄, Na₂HPO₄, NaH₂PO₄, Na₂CO₃, NaHCO₃, K₂CO₃,or NaB₄O₇.
 4. The process of claim 3 wherein the buffer is Na₃PO₄. 5.The process of claim 3 wherein the buffer is Na₂CO₃.
 6. The process ofclaim 3 wherein the buffer is K₂CO₃.
 7. The process of claim 3 whereinthe molar concentration of buffer in the aqueous phase is at least equalto the number of moles of M₂S_(n) or MHS present.
 8. The process ofclaim 1 wherein the weight percent of the phase transfer catalyst to thesilane compound is 0.1 to 10%.
 9. The process of claim 1 wherein theweight percent of the phase transfer catalyst to the silane compound is0.5 to 3%.
 10. The process of claim 1 wherein there is a 2.0 to 2.1molar excess of the (RO)_(3−m)R_(m)Si—Alk—X silane compound to thesulfide compound.
 11. The process of claim 1 wherein the molar ratio ofsulfur to the sulfide compound is 0.3 to
 5. 12. The process of claim 1wherein the molar ratio of sulfur to the sulfide compound is 2.7 to 3.2.13. The process of claim 1 wherein the weight percentage of water in theaqueous phase to the silane compound is 2.5 to 70%.
 14. The process ofclaim 1 wherein the weight percentage of water in the aqueous phase tothe silane compound is 20 to 40%.
 15. The process of claim 1 wherein thesilane compound is selected from chloropropyl triethoxy silane,chloropropyl trimethoxy silane, chloroethyl triethoxy silane,chlorobutyl triethoxy silane, chloroisobutylmethyl diethoxy silane,chloroisobutylmethyl dimethoxy silane, and chloropropyldimethyl ethoxysilane.
 16. The process of claim 15 wherein the silane compound ischloropropyl triethoxy silane.
 17. The process of claim 1 wherein thesulfide compound is selected from Na₂S, K₂S, Cs₂S, (NH₄)₂S, Na₂S₂,Na₂S₃, Na₂S₄, Na₂S₆, K₂S₂ K₂S₃, K₂S₄, K₂S₆, and (NH₄)₂S₂.
 18. Theprocess of claim 17 wherein the sulfide compound is Na₂S.
 19. Theprocess of claim 1 wherein the sulfide compound is selected from NaHS,KHS, and N₄HS.
 20. The process of claim 19 wherein the sulfide compoundis NaHS.
 21. The process of claim 1 wherein the phase transfer catalystis a quaternary onium salt.
 22. The process of claim 21 wherein thephase transfer catalyst is tetrabutyl ammonium bromide.
 23. A processfor the production of organosilicon compounds of the formula(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m) where R isindependently a monovalent hydrocarbon of 1 to 12 carbon atoms; Alk is adivalent hydrocarbon of 1 to 18 carbon atoms; m is an integer of 0 to 2,n is a number from 1 to 8, comprising: (A) reacting, a phase transfercatalyst, a sulfide compound having the formula M₂S_(n) or MHS, where His hydrogen, M is ammonium or an alkali metal, n is the same as above,water, a buffer and, optionally sulfur, to form an intermediate reactionproduct; (B) reacting said intermediate reaction product with a silanecompound of the formula; (RO)_(3−m)R_(m)Si—Alk—X where X is Cl, Br or I,and m is the same as above.
 24. The process of claim 23 wherein thesilane compound is dispersed in an organic solvent selected fromtoluene, xylene, benzene, heptane, octane, decane, and chlorobenzene.25. The process of claim 24 wherein the organic solvent is toluene. 26.The process of claim 23 wherein the reaction of said intermediatereaction product with the silane compound is conducted at a temperaturein the range of 40 to 110° C.
 27. The process of claim 23 wherein thereaction of said intermediate reaction product with the organic phasecontaining the silane compound is conducted at a temperature in therange of 60 to 95° C.
 28. A process for the production of organosiliconcompounds of the formula:(RO)_(3−m)R_(m)Si—Alk—S_(n)—Alk—SiR_(m)(OR)_(3−m) where R isindependently a monovalent hydrocarbon of 1 to 12 carbon atoms; Alk is adivalent hydrocarbon of 1 to 18 carbon atoms; m is an integer of 0 to 2,n is a number from 1 to 8; comprising (I) reacting: (A) a sulfidecompound having the formula M₂S_(n) or MHS, where H is hydrogen, M isammonium or an alkali metal, n is as defined above, with (B) a silanecompound of the formula; (RO)_(3−m)R_(m)Si—Alk—X where X is Cl, Br or I,and m is the same as above, and optionally, (C) sulfur in the presenceof a phase transfer catalyst and an aqueous phase containing a buffer toform a product mixture, (II) separating the organosilicon compound fromthe product mixture.
 29. The process of claim 28 wherein theorganosilicon compound is separated from the product mixture by (D)adding water or a dilute acidic solution to the product mixture, and (E)phase separating the product mixture into an organic phase containingthe organosilicon compound and an aqueous phase.
 30. The process ofclaim 28 wherein the weight percentage of water or dilute acidicsolution to the silane compound is 10-50%.
 31. The process of claim 28wherein the weight percentage of water or dilute acidic solution to thesilane compound is 20-40%.
 32. The process of claim 28 wherein theorganic phase containing the organosilicon compound is dried.
 33. Theprocess of claim 32 wherein the organic phase containing theorganosilicon compound is dried by heating the organic phase at reducedpressures.
 34. The process of claim 32 wherein the organic phasecontaining the organosilicon compound is dried by contacting the organicphase with a solid desiccant.
 35. The process of claim 34 wherein thesolid desiccant is sodium sulfate or magnesium sulfate.
 36. The processof claim 35 wherein the desiccant is sodium sulfate.
 37. The process ofclaim 28 further comprising the steps; (F) cooling the organic phasecontaining the organosilicon compound below 15° C. to precipitateun-reacted sulfur compounds, (G) separating the organic phase containingthe organosilicon compound from the precipitated un-reacted sulfurcompounds.
 38. The process of claim 37 wherein the organic phasecontaining the organosilicon compound is cooled to a temperature in therange of −20 to 10° C.
 39. The process of claim 37 wherein the organicphase containing the organosilicon compound is cooled to a temperaturein the range of −15 to −10° C.